The use of various types of biologically active cells as components of implanted devices for the purpose of delivering bioactive agents produced by said cells is well known in the art. Various attempts to devise methods for enhancing the survivability of such implanted cells have ultimately fallen short and require either the vascularization of the implant or a maximum diffusion distance of about 2-3 mm in order to provide nutrients to the cells. These various types of cells include fibroblasts, myoblasts, stem cells, progenitor cells, mature differentiated tissue cells, and undifferentiated cells.
Chondrocytes offer several unique advantages as vehicles for expressing therapeutic agents over other cell types. For example, chondrocytes do not require vascular support, and therefore can readily be used in environments that have a reduced, or non-existent vascularization system. Furthermore, chondrocytes are able to survive in harsh in vivo environments, including low pH and low oxygen surroundings. In addition, there is a reduced likelihood of malignancy due to the anti-angiogenic properties of normal chondrocytes. Chondrocytes also possess an immune privileged property which reduces immune rejection of co-implanted allogenic or xenogenic tissue. Furthermore, chondrocytes are more easily scalable compared to other normal untransformed cell strains. The genetic alteration of chondrocytes to express therapeutic agents for the treatment of pathologies or injuries other than cartilage tissue have been discussed by assignee's co-pending patent applications United States Published Application Nos. 2005/0054595 and 2006/0292131, which are herein incorporated by reference in their entirety.
However, there remains a need for devices and methods capable of delivering a large volume of such genetically-altered chondrocytes to various treatment sites not typically associated with chondroctyes.